Today the choice of engine oil is not a simple exercise, even within a single marque like BMW. Different engine families have different requirements, and those requirements are spelled out in great detail in BMW service literature.
BMW cooling systems have been keeping repair technicians and enthusiasts busy for a long time. Cooling system issues almost seem like the Achilles heel for BMW vehicles as they are quite common. As far back as the E30, clogged radiators and blown coolant hoses were common.